The present invention relates to a reflective article comprising a substrate sheet and a retroreflective sheet fixed on a major surface of the substrate sheet. The article can be adhered to an object such as a wall inside a tunnel, a guardrail, or a sign, to enhance visibility of the object during the night. In particular, the present invention relates to a reflective article having a reflective surface having substantially flat base portions and a plurality of protrusions being partitioned off by the base portions and protruding toward the retroreflective sheet which provide excellent wide incidence properties such as visibility of incident rays in a wide range.
There are conventionally known reflective articles such as a reflective sheet and a plate having a reflective surface including substantially flat base portions covered by a retroreflective sheet and a plurality of protrusions covered by a retroreflective sheet. For example, Japanese Utility Model Publication 62-41804 discloses a reflective sheet having protrusions formed on the surface to prevent paper from adhering to the sheet. The reflective sheet is produced by, for example, pasting a retroreflective sheet on a surface of a substrate sheet and subjecting the sheets to embossing to form protrusions on its surface. However, the size of each of the protrusions is relatively small (for example, 2 mm in width and 1 mm in height). Further, the publication does not disclose dimensions or arrangement of the protrusions in a reflective sheet which provide wide incidence reflection properties.
International Publication Nos. WO97/01677 and WO97/01678 disclose retroreflective article which is not subjected to embossing but is covered with a retroreflective material and is provided with a reflective wall-like protrusions and a flat surface. In this reflective article, dimensions and arrangement of the protrusions can be selected so as to improve wide incidence reflection properties. The above wall-like protrusions are formed continuously so as to surround the flat surface. Incidentally, the protrusions are formed continuously so as to surround the flat surface that makes removal of a water drop or a solid foreign matter adhering to the flat surface relatively difficult.
On the other hand, Japanese Patent Laid-Open 10-333616 discloses a reflective plate which is formed by subjecting a laminate containing a substrate sheet and a retroreflective sheet fixed on a surface of the substrate sheet to embossing and which has a substantially flat base portion covered with a retroreflective sheet and a reflective surface covered by a retroreflective sheet and having a plurality of protrusions separately disposed via the base portion. The plurality of protrusions are arranged so as to form a regularly-repeated geometrical plane pattern. This publication discloses a mode in which the above protrusions are separately arranged via the base portion and are not wall-like protrusions formed continuously so as to surround the flat surface. In such a mode, it is very easy to remove a water drop or a solid foreign matter adhering to the flat surface.
As the above Japanese Patent Laid-Open 10-333616 discloses, it is necessary for the reflective protrusions to have predetermined sizes and a predetermined pattern of arrangement so as to form a sheet-shaped or a plate-shaped reflective article excellent in wide incidence reflection properties. Particularly, this is important to improve reflection properties to rays having a relatively high incidence (for example, 70xc2x0 or more to the normal line to the reflective surface). When a reflective article is used as a constituent member of a marking used in the open air, solid foreign matter such as dust sticking to a reflective surface should easily be removed by a washing operation (or a cleaning operation). Thus, sufficient recovery of desired properties such as reflection brightness is possible.
Washing a reflective article manually using a wash apparatus is effective in the aforementioned washing operation (or the cleaning operation). Such a wash apparatus is used by spraying water under high pressure to the reflective surface of a reflective article, or blushing the reflective surface with a cleaning member such as a brush. For example, when a reflective article is fixed on a surface of an inner wall of a tunnel, the reflective article is washed simultaneously with the inner wall by a washing device which sprays water under high pressure and washes the inner wall of the tunnel.
However, in a reflecting element in which a retroreflective sheet is adhered on a substrate sheet, the retroreflective sheet is delaminated from a substrate sheet in an edge portion (a frame portion located at the end of the retroreflective sheet in a direction toward inside the reflective surface) by the aforementioned washing operation. In particular, when the retroreflective sheet has a direction of length and a direction of width, delamination in the end portion in a direction of width having a relatively long dimension is remarkable.
Therefore, the present invention aims to provide a reflective article and a method for manufacturing the reflective article capable of effectively preventing an end portion of a retroreflective sheet from delamination and exfoliating from a substrate sheet by a washing operation.
The present disclosure is directed to a reflective article comprising a substrate sheet, and a retroreflective sheet covering a surface of said substrate sheet, wherein the reflective article is provided with substantially flat base portions and a plurality of protrusions being partitioned off by said base portions and protruding toward said retroreflective sheet. Delamination of said substrate sheet and said retroreflective sheet from each other is prevented by folding back at least a part of an edge of one of the sheets so as to wrap at least a part of an edge of the other sheet therein in a condition that the reflective article is fixed to at least a surface of an object. The above reflective article may be one in which both of the substrate sheet and the retroreflective sheet have directions of length and width, and at least one of portions around edges in a direction of width of the substrate sheet is fold back on the side of the retroreflective sheet.
Another aspect of the disclosure is a method for manufacturing a reflective article, comprising the steps of preparing a flat substrate sheet made of metal having drawing elongation ability of resin, forming a laminate by fixing a retroreflective sheet to a surface of said substrate sheet, wherein the retroreflective sheet has a shorter width than the substrate sheet, and a foldable portion elongated along the direction of width of the substrate sheet in a portion around an edge in a direction of width of the substrate sheet when the retroreflective sheet is attached to the substrate sheet, forming a folded portion by folding said foldable portion toward the side of the surface covered with said retroreflective sheet of the substrate sheet so as to cover in and around an end portion of said retroreflective sheet, subjecting the laminate to embossing by abutting an emboss tool having a plurality of bosses against the other surface of the substrate sheet to give said protrusions.
In the present specification, xe2x80x9cfolding back at least a part of an edge of one of the sheets so as to wrap at least a part of an edge of the other sheet thereinxe2x80x9d means the following conditions:
(i) A frame (an edge portion and its vicinity) of the above retroreflective sheet is covered by a folded portion formed by folding a frame (an edge portion and its vicinity) of the substrate sheet, or
(ii) A frame (an edge portion and its vicinity) of the above substrate sheet is covered by a folded portion formed by folding a frame (an edge portion and its vicinity) of the retroreflective sheet.
Between the above two modes, (i) is preferable. The reason is that a retroreflective sheet used in the present invention usually has a cover layer of a light-transmitting film which covers a surface made of a reflective article such as beads or a reflective article made of a light-transmitting film (cube corner prism etc.). Such a light-transmitting film of the retroreflective sheet is prone to break when the retroreflective sheet is folded to make a relatively acute angle in the aforementioned manner. Therefore, the above mode (i) in which the retroreflective sheet is not folded is preferable. Though a folded portion may be formed after the reflective article is fixed to a surface of an object in the above mode (i), the folded portion is generally formed before the reflective article is fixed to a surface of an object.
The substrate sheet generally has a relatively longer length than a width. However, the length may be almost the same as the width as long as it does not impair the effect of the present invention. Though the retroreflective sheet generally has a relatively larger length than a width, the length may be almost the same as the width as long as it does not impair the effect of the present invention. A reflective article having a substrate and/or a retroreflective sheet having such dimensions generally has a relatively larger length than width, the length may be almost the same as the width as long as it does not impair the effect of the present invention.
The shape of the reflective protrusions is not particularly limited as long as it does not impair the effect of the present invention. However, it is preferable that the protrusions are continuously arranged from one end of the retroreflective sheet in the direction of the width to the other end thereof so as to form a line of protrusions. Such a line of protrusions has a reflective side surface (surface of a reflective sheet protruded in regard to a base portion) which is substantially perpendicular to the longitudinal direction and capable of reflecting a ray of light incident upon a wide reflective side surface. Therefore, a reflection brightness in the case that a reflective article is disposed on so that the longitudinal direction of the reflective article is substantially parallel to the road can be enhanced particularly effectively.
It is preferable to produce a reflective article having a line of protrusions by a method comprising the steps of:
(a) preparing a flat substrate sheet made of metal having drawing elongation ability of resin, (b) forming a laminate by fixing a retroreflective sheet to a surface of said substrate sheet so as to have shorter length in a direction of width than that of the substrate sheet and to have a foldable portion elongated along the direction of width of the substrate sheet in a portion around an edge in a direction of width of the substrate sheet when the retroreflective sheet is fixed to the substrate sheet, and (c) forming a folded portion by folding said foldable portion toward the side of the surface covered with said retroreflective sheet of the substrate sheet so as to cover in and around an end portion of said retroreflective sheet, and (d) subjecting the laminate to embossing by abutting an emboss tool having a plurality of bosses against the other surface of the substrate sheet to give said protrusions.
In this method, a substrate sheet is subjected to folding prior to embossing which is a process for providing protrusions having a shape of a line or the like. Because folding is performed on the end portions of a retroreflective sheet and a substrate sheet are flat, the protrusions on the reflective surface do not hinder folding of the substrate sheet, which makes the folding operation easy. When the protrusions are not present in the edge portion of the reflective sheet (e.g. the protrusions are not arranged in line but on a plurality of dots regularly arranged on the reflective surface) and do not hinder folding of the substrate sheet, folding may be performed after embossing.